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CHARACTERISTICS OF CRASHES IN WHICH A VEHICLE OVER TURNS

The objective of this study is to identify the characteristics of overturning crashes that might be susceptible to correction or amelioration through the application of highway and traffic engineering principles. The study first analyzed information contained in the Fatal Accident Reporting System and then analyzed data from New Mexico, which has one of the nation's highest rates of fatal overturning crashes. National statistics report that overturning is involved in 4 percent of all crashes but in 10 percent of fatal crashes. This study found that, in 11 states, more than 20 percent of the fatal crashes involved over-turning. By use of appropriate statistical techniques, the study determined that, in comparison with other crash classifications, overturning occurs with significantly higher frequency under adverse geometric, weather, and lighting conditions. Overturning crashes are also more likely to involve nonlocal drivers and vehicls other than passenger cars. The analysis showed that these crashes had significantly different characteristics than those associated with fixed objects. Therefore, many remedial actions undertaken to reduce fixed-object crashes will have minimal impact on overturning. It is hypothesized that better application of delineation and warning devices could have a positive effect on overturning crash experience in addition to improvements in roadway geometrics. Some roadside design standards may need modification to accommodate the special requirements of certain vehicles. A field study of overturning crash sites is being conducted to obtain more detailed roadway and environmental information on these locations.